As a wheel center bore directly matches with an automobile spindle in connection size, the size of the wheel center bore generally needs to be strictly controlled in a wheel machining production process. According to the traditional control method, an operator holds a go/no go gauge to perform 100% detection on the wheel center bore. However, by virtue of continuously improved automatic production mode, such detection mode obviously already cannot fit to modern production. Therefore, it needs an automatic detection device to achieve the full automation online detection requirement of the key size.